/**
 * @file   Common.cpp
 * @author Djuro Drljaca (djurodrljaca@gmail.com)
 * @date   2013-03-10
 * @brief  DataBus Common.
 *
 * Copyright (C) 2013  Djuro Drljaca <djurodrljaca@gmail.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 *
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <DataBus/Common/Common.h>

static const quint8 s_crcTable[256] =
{
    0, 94, 188, 226, 97, 63, 221, 131, 194, 156, 126, 32, 163, 253, 31, 65,
    157, 195, 33, 127, 252, 162, 64, 30, 95, 1, 227, 189, 62, 96, 130, 220,
    35,  125, 159, 193, 66, 28, 254, 160, 225, 191, 93, 3, 128, 222, 60, 98,
    190, 224, 2, 92, 223, 129, 99, 61, 124, 34, 192, 158, 29, 67, 161, 255,
    70, 24, 250, 164, 39, 121, 155, 197, 132, 218, 56, 102, 229, 187, 89, 7,
    219, 133, 103, 57, 186, 228, 6, 88, 25, 71, 165, 251, 120, 38, 196, 154,
    101, 59, 217, 135, 4, 90, 184, 230, 167, 249, 27, 69, 198, 152, 122, 36,
    248, 166, 68, 26, 153, 199, 37, 123, 58, 100, 134, 216, 91, 5, 231, 185,
    140, 210, 48, 110, 237, 179, 81, 15, 78, 16, 242, 172, 47, 113, 147, 205,
    17, 79, 173, 243, 112, 46, 204, 146, 211, 141, 111, 49, 178, 236, 14, 80,
    175, 241, 19, 77, 206, 144, 114, 44, 109, 51, 209, 143, 12, 82, 176, 238,
    50, 108, 142, 208, 83, 13, 239, 177, 240, 174, 76, 18, 145, 207, 45, 115,
    202, 148, 118, 40, 171, 245, 23, 73, 8, 86, 180, 234, 105, 55, 213, 139,
    87, 9, 235, 181, 54, 104, 138, 212, 149, 203, 41, 119, 244, 170, 72, 22,
    233, 183, 85, 11, 136, 214, 52, 106, 43, 117, 151, 201, 74, 20, 246, 168,
    116, 42, 200, 150, 21, 75, 169, 247, 182, 232, 10, 84, 215, 137, 107, 53
};

quint8 DataBus::calculateChecksum(const QByteArray &data,
                                  const int startIndex,
                                  const int size,
                                  bool *ok)
{
    // Check input parameters
    if ((startIndex < 0) ||
        (startIndex >= data.size()))
    {
        if (ok != 0)
        {
            *ok = false;
        }

        return 0;
    }

    if (data.size() == 0)
    {
        if (ok != 0)
        {
            *ok = false;
        }

        return 0;
    }

    if ((size == 0) ||
        (size < -1) ||
        ((startIndex + size) > data.size()))
    {
        if (ok != 0)
        {
            *ok = false;
        }

        return 0;
    }

    // Calculate checksum
    quint8 checksum = 0;
    int count = size;

    if (count == -1)
    {
        count = data.size() - startIndex;
    }

    for (int i = 0; i < count; i++)
    {
        quint8 byte = (quint8)data.at(startIndex + i);

        checksum = s_crcTable[checksum & byte];
    }

    // Return calculated checksum
    if (ok != 0)
    {
        *ok = true;
    }

    return checksum;
}
